It took some gall

Quercus robur, the 'English' oak, is the most hospitable of trees providing protection, nourishment and congenial living conditions for a whole range of plant, fungus and animal species. A large old oak acts as a veritable ecosystem of its own. But smaller scrub oaks in the hedges and plantations can host a rich array of galls such as the two I spotted here today.

(Plant galls are abnormal growths of plant cells formed as a response to the stimulus caused by an insect laying eggs, or larvae feeding, in the tissues of the plant and can affect leaves, stems, buds, flowers or fruit.)

Top left is an artichoke gall caused by the tiny wasp Andricus fecundator laying an egg in a leaf bud which then swells and takes the 'artichoke' form. The hard gall within eventually fall to the ground leaving the external structure (seen below) to wither on the twig. The larva develops in the fallen gall and in the spring an asexual form of the wasp emerges and lays her parthenogenetic eggs in (male) oak catkins which turn into another sort of gall from which will emerge a sexual form of the wasp, which after mating, will start the cycle again. (And we thought our sex lives were complicated?)

Top right are the more familiar oak marble galls created by the egg deposition of another gall wasp Andricus kollari which has a similar two year sexual/asexual reproductive cycle. These marble galls contain tannin and were once used to make the black writing ink that was used for manuscripts from the 12th to the 20th century (and even further back for the Dead Sea Scrolls).

It was a complicated process - this is a recipe from 1596

To Make Ink to Write Upon Paper
Take half a pint of water, a pint wanting a quarter of wine, and as much vinegar, which being mixed together make a quart and a quarter of a pint more, then take six ounces of galls beaten into small powder and sifted through a sieve, put this powder into a pot by itself and pour half the water, wine and vinegar into it, take likewise four ounces of vitriol, and beat it into powder, and put it also into a pot by itself, wherein put a quarter of the wine water and vinegar that remains and to the other quarter put four ounces of gum Arabic beaten to powder, that done cover the three pots close and let them stand three or four days together, stirring them every day three or four times. On the first day set the pot with the galls on the fire, and when it begins to seeth, stir it about till it be thouroughly warm, then strain it through a cloth into another pot, and mix it with the other two pots, stirring them well together, and being covered, then let it stand three days, til you mean to use it. On the fourth day when it is settled pour it out and it will be good ink.

(This strikes me as a great excuse for procrastination when you have a writing deadline. You'd have to start by going to the woods to collect the galls - although European marble galls are rather low in tannic acid and it was Aleppo galls that were the most desirable).

Bottom right: the little doughnut shapes between the two acorns look like galls but are not. They are the embryonic rudiments of unfertilised flowers.